Tube Failure question

Keep the Bryston preamp! I have one in use right now. Excellent SQ! Don't fall for the false belief that only tube circuits are "musical"!

Not true for vacuum tubes you get with stock amps are not verygood vs the originals from 1970 on down .the vacuum is of the gasses the inspection of the grids on average over 10 % variances inside gridsor more   years ago 2-3% was common 
the materials not even close maybe 3000 hours  on average NOS tubes from the 50s many times 10,000 hours , some rectifiers run for10 years . Emissions labs in Europe are great as well as a few others for premium brands . Call vacuum tube services, or Brent Jesse recordings to get true New  closely matched vacuum tubes a big upgrade in sound also..I grew up on all the classic tubes and the  majority of Chinese, and Russia tubes are average at best compared.

Quad of Tung Sol 7581A for around $100 will sort you out. Search this forum for more info.

Thanks to all for the advice as I said I am new to tubes so dont really know the pros and cons of different tubes. 
I have not contacted Primaluna but will now thanks to the advice here.
The small tubes I have are 12AU7 and the large ones are KT 88. 
I see suggestions for EL 34 and Tung Sol 7581 Can someone give me there thoughts on the differences between them and KT 88? 
Lastly the noise does sound as if the amp is clipping (popping) but is not consistant. Am I right to assume tubes?
Can I but tubes somewhere in Canada? I am in Ontario.
Thanks again.
Tom

Forgot to say the amps are Prologue 7 mono blocks
The issue I have is intermittent but increases with volume. This makes it hard to change out tubes to test.
I have heard I should wear gloves to touch the tubes is this correct?